This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Smooth pursuit (SP) eye movements are used to maintain the image of a moving object on or near the fovea. The SP system is able to adapt to challenges associated with development or injury to maintain pursuit accuracy and clear vision. The macaque cerebellum is known to play a role in adaptive changes of SP, however, the sources of signals for smooth pursuit adaptation have not been defined. Our studies are directed at structures that form part of the afferent limb pretectal pathways that provide visual- and eye-motion signals to the cerebellum for smooth pursuit. We examined the role of the pretectal nucleus of the optic tract (NOT), which provides retinal error information to the cerebellum by way of the inferior olivary nucleus. We delivered a brief (200ms) train of micro-electrical stimulation (ES) in the NOT to introduce directional error signals. Our results indicated that the NOT is an important source of visual error signals leading to adaptive plasticity in smooth pursuit. Using pharmacological inactivation we also found that inactivation of the pretectal nucleus of the optic tract (NOT) significantly impaired smooth pursuit adaptation. During the next year we test the hypothesis that NRTP and DLPN provide different eye movement signals that interact with visual motion signals provided by the NOT to produce direction selective adaptation. Our studies will significantly advance our understanding of how the brain adapts smooth pursuit behavior in the face of challenges associated with development, aging or injury. This information is important for improving diagnosis and treatment options for subjects with impaired visual-oculomotor function.